1. Field of the Invention
The present invention relates to a method of manufacturing semiconductor devices. More particularly, the present invention relates to a process of stripping photoresist from a semiconductor wafer using a solution of dimethylacetamide or a solution of monoethanolamine and dimethylsulfoxide.
2. Description of the Related Art
In general, the fabricating of semiconductor devices involves the use of photolithography for forming a pattern on a semiconductor wafer.
In photolithography, a photoresist deposited on the semiconductor wafer is selectively removed in a series of processing steps, such as an exposure step, a development step, etc. A pattern designed according to the desired characteristics of the semiconductor device is formed on the semiconductor wafer using the photoresist as a mask.
Photoresists can be classified into two groups: positive photoresists and negative photoresists. Whether a photoresist is considered to be of a positive type or of a negative type depends on the region thereof which is removed after selected portions of the photoresist are irradiated during the exposure process.
That is, the positive type of photoresist is one in which the exposed regions of the photoresist are removed from the semiconductor substrate. The negative type of photoresist is one in which the non-exposed regions of the photoresist are removed from the semiconductor substrate.
On the other hand, photoresists can also be classified according to the wavelength at which the photoresist responds with respect to its exposure and development. Photoresists classified in this way include those of the I-line group, the G-line group, and the Deep-UV group.
When an Hg-Arc lamp is used as the general light source in the semiconductor device manufacturing process, photoresists are classified in the I-line group, G-line and Deep-UV according to the wavelength of light from the spectrum of the Hg-Arc lamp. More specifically, a photoresist in the I-line group responds to light having a wavelength of 365 nm. A photoresist in the G-line group responds to light having a wavelength of 436 nm, and a photoresist in the Deep-UV group responds to light having a wavelength of 248 nm.
In a conventional semiconductor device fabrication process, a positive photoresist in the I-line group is normally used. That is, the regions of a photoresist exposed to light having a wavelength of 365 nm are selectively removed from the semiconductor substrate.
However, photolithography using a positive photoresist in the I-line group has its limits. In particular, such a process can only form a pattern as small as 0.3 .mu.m. Such a process, therefore, is not suitable for manufacturing the highly miniaturized semiconductor devices which are now in demand.
Accordingly, recent semiconductor device fabrication processes employ photoresists in the Deep-UV group. These photoresists can be used to form patterns smaller than even 0.2 .mu.m.
However, photoresists in the Deep-UV are inferior to those in the I-line group in terms of their resistance to light and heat. This is because the constituents of the photoresists in the I-line group and the photoresists in the Deep-UV group, such as the polymer component, the light-reactant, and the solvent, are different from each other.
In fact, photoresists in the Deep-UV group are not widely used in semiconductor device fabrication because no chemical has yet been developed which can completely remove a Deep-UV group photoresist remaining on a semiconductor substrate after the photolithography has been completed.